The story of Avunu revolves mainly around Mohini (Poorna) and her husband Harsha (Harshavardhan Rane). They are a newly married couple and they settle down in a gated community near Gandipet called ‘Classic Homes’. Very soon, strange and unexplained phenomena are observed in the house. A ghost / spirit starts stalking Mohini and takes voyeuristic pleasure in watching her nude while dressing up etc.

Meanwhile, their neighbors have a small kid, Vicky, who claims to be able to speak to his dead grandfather. Vicky seems to see the spirits of departed souls but no one believes him. He claims that the spirit of Captain Rao is in the house of the newlyweds.

Harsha and Mohini make plans to go for a honeymoon to Paris. But things take an ugly turn once the ghost decides to start getting aggressive in its overtures towards Mohini. The shell shocked young lady attempts to flee from the evil spirit, but all her attempts are blocked.

Slowly, Vicky’s parents and the people around Mohini realise that the spirit of Captain Rao is real and they must do all they can to save her. Will they be successful? Who is Captain Rao? That forms the story.